Generally, in the industrial synthesis of a methanol, carbon monoxide and hydrogen (synthesis gas) obtained by steam reforming of a natural gas mainly comprising methane are used as the starting materials and the synthesis is performed using a copper/zinc-type catalyst or the like by a fixed-bed gas phase method under severe conditions of 200–300° C. and 5–25 MPa. Although this reaction is an exothermic reaction, efficient heat extraction can be hardly attained because of poor thermal conductivity in the gas phase method and a process of lowering the one-pass conversion and recycling unreacted high-pressure starting material gas is employed, which has, however, a severe problem in the efficiency. Despite such a problem, the fixed-bed gas phase method is not easily prone to the reaction inhibition by water or carbon dioxide contained in the synthesis gas and various plants are now operated by making use of this advantageous property.
On the other hand, various methods of synthesizing methanol in a liquid phase and thereby increasing the heat extraction rate are being studied. Among these, a method using a catalyst having high activity at low temperatures (approximately from 100 to 180° C.) is advantageous to the production system also in view of thermodynamics and being taken notice of. However, this method has been reported to suffer from quick decrease in the activity due to water and carbon dioxide contained in many cases in the synthesis gas and not used in practice.